parts of a cnidarian

Parts of a Cnidarian Biology Three Part Cards

Claudia Medina

Montessori Creative 2014


Parts of the Cnidarian

Cnidarians are almost exclusively predators, catching and eating other animals. The characteristic feature of the groups, their cnida, is devices through which they capture prey: they might deliver a paralyzing sting, a capturing harpoon and cable, or a tangling net. The poisonous sting, called nematocysts, is the most common type of cnida. The old name for the phylum was Coelenterata, a name based upon their internal space, but there was nothing especially unique about that structure, while cnidae, the basis for the new name, are not found in any other group.

cnidarians


Some species of jellyfish posses a stinging structure in the form of nematocysts, which are generally concentrated on the tentacles, or oral arms of the jellyfish. This venomous apparatus although toxic are primarily a jellyfishes defense and means of hunting for prey. While in most species the stings usually paralyze or kill only small creatures, some poses doses that are harmful to humans also. However, jellyfish do not attack humans.

Despite what may be common belief the tentacles of jellyfish are not involved at all in the swimming or movement action of the jellyfish. These tentacles are used only for gathering food and stinging potential attackers.

nematocysts oral arms


Jellyfish named for their jelly-like body resembling an empty plastic bag come in a wide variety of sizes, shapes and colors. Most are semi-transparent or glassy and bell-shaped, measuring less than an inch to over a foot across the bell, although some may reach 7 feet. Jellyfish move by floating and relying on the oceans currents and winds. Jellyfish move by squeezing their bodies so that jets of water from the bottom of their bodies are pushed out which in turn causes the jellyfish to be propelled forward.

In addition to envenoming prey, cnidarians use their tentacles to bring their food towards their mouth or anus and to provide defense against predators.

Jellyfish tentacles


The body of the jellyfish mainly consists of a bell which confirms to radial symmetry. It radiates from the central axis and is perfectly symmetrical from all sides. This perfect symmetry is very useful for the survival of the jellyfish because it allows jellyfish to detect food as well as protect itself from predators from all sides.

The bell of the jellyfish consists of an outer layer called the epidermis and an inner layer called the gastrodermis. The epidermis contains nerves that can detect light, odor, pressure and other stimuli. The nerve receptors in the epidermis are not controlled by any brain

body The bell


A layer of jelly-like material between the

external (ectoderm) and internal (endoderm) cellular layers of the body of a sponge or cnidarian. The mesoglea consists

largely of collagen-like fibers . The Mesoglea acts as the creatures'

structural support in water, as they lack bones, cartilage or other more common means of support. Because it is a liquid,

these creatures tend to collapse on land.

Mesoglea

parts of a cnidarian

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